Firearm



Sept. 28, 1937. M. M. JOHNSON, JR

FIREARM 2 Sheets-Sheet l Filed April 2, 1936 lwezzzo 2' Patented Sept.28 i193? UHTED 8 Claims.

This invention relates to firearms of the semiautomatic type having abolt slldably mounted for a reciprocating stroke between a rearwardopen-breach position and a forward unlocked position, at least a portionof the bolt being rotatable from unlocked to locked position, and havingmeans for feeding cartridges into position to be pushed into the firingchamber during the forward stroke of the bolt. Theinvention isespecially applicable to firearms in which the bolt is locked to areciprocating barrel and unlocked in response to or by virtue of aslight recoil of the barrel.

Objects of the invention are to provide automatic breech mechanism whichhas sufiicient strength to function indefinitely with high-powerammunition, to facilitate the feed of cartridges to the firing chamber,to improve the locking and unlocking action of the bolt, to simplify thecon struction of firearms of the type referred to and generally toimprove the art of semi-automatic firearms.

in one aspect the present invention, involves a bolt having at itsforward end a locking head provided with one or more circumferentialrows of locking lugs which move in front of locking ,abutments when thehead is rotated into locking position, the bolt having a recess behindthe looking lugs to accommodate the aforesaid abutments and the radialdimensions of the bolt, at least on the side from which the cartridgesare supplied, are approximately the same forwardly and rearwardly of therecess, whereby the feed of cartridges to the firing chamber isfacilitated.

In another aspect the invention relates particularly to firearms of theaforesaid recoilingbarrel type, involving improved means for rotatingthe locking lugs into and out of locking position behind the aforesaidlocking abutments which, in this aspect, are on' the recoiling barrel.The rotating portion of the bolt (which preferably constitutes theentire bolt) is provided with a cam surface engageable with a. camsurface. on the receiver to cam the bolt from locked to unlockedposition as the bolt and barrel recoil together, after which the boltcontinues to move to fully retracted position in response to theresidual gas pressure and to some extent its own inertia. The angularityand circumferential extent of the receiver cam, the friction of thesliding surfaces, and the inertia of the moving parts are preferablycorrelated so that the bolt is not fully unlocked until after theprojectile has left the barrel and after the gas pressure has decreasedto a safe.

excessive force. To return the locking lugs to locked position, at theend 'of the forward stroke of the bolt, the rotary portion of the boltis pro-- vided with another cam surface, engageable with a cam surfaceon the bolt pusher between the bolt and recoil spring, to rotate thelocking lugs into locking position in front of the locking abutments onthe barrel. Preferably the locking and unlocking cam surfaces on thebolt are provided on opposite sides of a lug on the bolt which slides ina slot. in the receiver adapted to prevent rotation of the bolt exceptat the forward end of its reciprocating stroke.

For the purpose of illustration. a typical embodiment of the inventionis shown in the accompanying drawings in which,

typ

Fig. 2 is a section on line 2-2 of Fig. 1;

Fig. 3 is a section on line 3--8 of Fig. 1;

Fig. i is a section on line 4l-l of Fig. 2;

Fig. 5 is a section on line 5-5 of Fig. 3; v

Fig. 6 is a front elevation of the bolt;

Fig. '7 is a top plan view of the bolt and pusher showing the barrel inaxial section;

Fig. 8 is a similar view showing the bolt in locked position;

Fig. 9 is a bottom plan view of the barrel and receiver with partsbroken away;

Fig. 10 is a section on line l@l of Fig. 9 and Fig. 11 is a verticalaxial section through the forward end of the receiver and stock'showingthe barrel in side elevation.

The particular embodiment of the invention chosen for the purpose ofillustration comprises a stock having a rear butt portion l and aforward portion 2 extending under the receiver, a frame in the form of areceiver having a rearward portion 3to accommodate the bolt and aforward her in the forward stroke of the bolt.

The barrel has a limited degree of longitudinal movement in the receiverfrom the forward. position shown in Fig. 9 to a rearward position inwhich the rear end of the barrel engages the shoulder 8 on the receiver(Fig. 9). Forward movement of the barrel is limited by a sleeve 9 (Fig.11) press-fitted on the barrel and engageable with a collar in threadedon the forward end. of the receiver. Rotary movement of the barrel inthe receiver is restrained by a depending lug Fig, 1 is a side elevationof a rifle of the Army H on the sleeve 9 and another lug l2 projectingdownwardly from the rear end of the barrel, both lugs sliding in a slotis in the lower side of the receiver. The lower end of lug H is providedwith a Socket i ii to receive the forward end of a compression spring43, the rear end of which seats against the bottom of an aligned socketin the stock 2 (Figs. 1 and 11). The rear end of the barrel is providedwith a circumferential row of interior locking abutments ill withalternate grooves l8 therebetween.

The forward end of the bolt 6 is provided with corresponding exteriorlocking lugs it for engagement in front of the locking abutments H, thecircumferential width of the lugs is approximating that of the abutmentsH and being slightly less than the width of the grooves 68 so as to passbetween the abutments it when the bolt is rotated to unlocked position.Immediately behind the locking lugs is the bolt is provided with anannular recess 20, the diameter of the bolt forwardly and rearwardly ofthis recess being approximately the same. Projecting from the top of thebolt near its rearward end is a cam lug 2i adapted to slide forwardlyand rearwardly in a groove 22 in the top of the receiver. At the forwardend of the stroke of the cam lug 2| the receiver groove 22 is providedwith a lateral recess 23 having a cam surface 24 engageable with the camsurface 25 on the lug 2|.when the bolt is rotated into locking position.On the other side of the'lug 2! is another cam surface 25 engageablewith a cam surface 26 at the forward end of the bolt-pusher 1.

The pusher 1 is yieldingly urged forwardly by a recoil spring 21 mountedin the butt I of the stock and kinematically interconnected with thepusher by means of links 28. The firing pin 29 projects rearwardlythrough the pusher l as shown in Figs. 4, 5, '7, and 8 and the hammer(not shown) moves into engagement with the bolt through a slot 30 in thebottom of the receiver and thence into the space between the two links28. The extractor 3! is integral with the bolt (Fig.6) and the ejector(not shown) projects into a slot 32 in the opposite side of the bolt,the rearward portion 32' of the slot being widened to accommodate therotary movement of the bolt (Figs. 2 and 3). The forward ends of thelocking lugs H] are fiush with the forward end of the bolt.

When the bolt is in locked position (Figs. 1, 3, 5, and 8) the lockinglugs 19 are in front of the locking abutments ll, thereby preventingendwise movement of the bolt relatively to the barrel, and the cam lug2! is in the recess 23 in the side of the receiver groove 22 as shown inFigs. 3 and 5. When the cartridge is fired the barrel and bolt recoiltogether and during this recoil movement the bolt is rotated to unlockedposition by interengagement between the surfaces 24 and 25 of thereceiver recess 23 and the cam lug 2| on the bolt. By this time theprojectile has left the barrel and the breech pressure has dropped to avalue which is little more than sufficient to retract the bolt to therearward end of the receiver against the action of the recoil spring 21.During the backward and forward movement of the bolt it is restrainedfrom rotation by the lug 2| in the receiver groove 22. As the boltreturns to its forward position it picks up a cartridge from themagazine (not shown because it is wholly within the stock) and when itreaches forward position the pusher 1 cams the bolt into lockingposition by virtue of the interengagement between the cam surfaces 25and. 26 on the lug 2i and the pusher 1 respectively. During the rearwardand forward stroke of the bolt the barrel is returned to its forwardposition by the spring l5. By making the diameters of the bolt onopposite sides of the annular recess 20 substantially equal, theuppermost cartridge 'in the magazine is maintained in proper alignmentfor feeding to the firing chamber substantially asit would if the boltwere cylindrical throughout its entire length.

It should beun-derstood that the present disclosure is for the purposeof illustration only and that this invention includes all modificationsand equivalents which fall within the scope of the appended claims.

I claim:

1, A firearm comprising in combination a barrel mounted to slidelongitudinally to a slight extent in response to recoil, stop means tolimit recoil of the barrel, a bolt coaxial with the barrel and alsomounted to slide in response to recoil but to an extent sufficient topermit introduction of a cartridge between the forward end of the boltand the rear end of the barrel, the bolt being provided at its forwardportion with a circumferentially extending row of spaced locking lugs,at least the forward portion of the bolt being rotatable to apredetermined extent, means preventing such rotation except when the.bolt is adjacent to firing pcsition, a row of locking abutments on thebarrel normally disposed to the rear of and engaging the locking lugs onthe bolt thereby to lock the barrel and bolt against relativelongitudinal movement, the engaging surfaces of the lugs and abutmentsbeing substantially perpendicular to the axis of the barrel, concealedunlocking means including complemental cams operative, during and inresponse to the short recoil movement of the barrel,

to rotate at least the head portion of the bolt sufiiciently todisengage the locking lugs of the bolt from those of the barrel therebyto permit the continued recoil movement of the bolt alone tobreech-opening position after the recoil movement of the barrel hasceased, the barrel being free to return to firing position immediatelyafter it is unlocked from the bolt, a recoil spring, a pusher actuableby the spring, at the completion of the recoil movement of the bolt, toadvance the bolt to breech-closing position, and relocking means,including complemental relatively movable rigid cams, one of which iscarried by the pusher and advances with the latter in response to theaction of the recoil spring, said unlocking means operatingautomatically as the bolt comes to rest at its extreme forward positionto rotate at least the forward portion of the bolt and thereby toreengage the locking lugs and abutments.

2. A firearm comprising in combination a frame and a barrel mounted toslide axially therein for a slight distance in response to recoilenergy, means limiting recoil movement of the barrel, a reciprocablebreech-opening and closing bolt coaxial with the barrel, said bolt beingrotatable to a predetermined angular extent when the bolt is adjacent tofiring position, the forward portion of the bolt being provided with acircumferential row of locking lugs with intervening grooves, the

rear end of the barrel having an axial bore of a diameter such as toreceive the forward end of the bolt, a row of spaced locking abutmentspro-' jecting inwardly from the wall of said bore and normally disposedto the rear of and engaging the locking lugs of the bolt, the engagingsurfaces tion at least of the bolt from locked to unlocked to firingposition immediately after the bolt has been unlocked from it, a recoilspring and pusher means actuated thereby and operative at the completionof the breech-opening movement of the bolt to return the latter tobreech-closing position, and a second cam on the bolt and a complementalcam carried by the pusher means operative, after the bolt reachesbreech-closing position, to rotate the bolt thereby to reengage thelocking lugs of the bolt with the abutments of the barrel.

3. In a firearm of the kind wherein a barrel and a coaxial breech blockare mounted to slide forwardly and rearwardly in guides in a supportingframe in response to recoil energy, the'barrel being arranged to slideto a slight extent concomitantly with the bolt and then to stop whilethe bolt continues its recoilmovement to cartridge-ejecting andreceiving position, means to prevent rotation of the barrel, the boltbeing rotatable to a predetermined degree, a reciprocatory bolt pusher,and a recoil spring urging said pusher forwardly, in combinationnormally contacting surfaces on the barrel and bolt respectively, saidsurfaces being substantially perpendicular to the axis of the barrel,for interlocking the two parts against relative endwise movement whenthe bolt is in the firing position, a cam lug on the bolt having two camsurfaces, a fixed cam on the frame cooperable with one of the camsurfaces of the bolt to turn the bolt from locked to unlocked positionin response to the aforesaid slight rearward recoil' movement of thebarrel in the frame, a cam on said pusher cooperable with the other camsurface of the bolt, after the bolt has completed its axial advancetofiring position, to turn the bolt from unlocked to locked position,and a spring operative to return the barrel to its forward positionimmediately upon release of the bolt from the barrel.

4. In a fiream r the kind wherein a barrel and a coaxially arrangedbreech block are mounted to recoil rearwardly in guides in a supportingframe in response to recoil energy, the barrel being arranged to slideto aslight extent concomitantly with the bolt and then to stop, andhaving provision for returning the barrel immediately to firing positionwhile the bolt continues its recoil movement thereby to open the breechfor the ejection and reception of cartridges, means to prevent rotationof the barrel, the forward portion at least of the bolt being rotatableto a predetermined degree but only while the bolt is adjacent to firingposition, a reciprocatory bolt pusher, and a recoil spring urging thepusher for,- wardly, in combination interengaging projections on thebarrel and bolt respectively for interlocking the barrel and boltagainst relative endwise movement 'when the bolt is in firing position,said interengaging projectionshaving their contacting surfaces disposedsubstantially perpendicular to the axis of the barrel, a rigid camsurface on the ,frame, an element on the bolt with which said camsurface cooperates to turn said forward porposition in response to theaforesaid slight rearward movement of the barrel in the frame, a rigidcam surface on the pusher, and a part on the bolt with which said lattercam surface cooperates, in response to the advance of the pusher by therecoil spring, to turn said forward portion at least of the bolt fromunlocked to locked position after the bolt has arrived at the extremeforward end of its path of movement.

5. In a firearm of the kind whereina barrel and a coaxially arrangedbreech block are mounted to recoil rearwardly in guides in a supportingframe in response to breech pressure, .the barrel being arranged toslide to a slight extent only concomitantly with the bolt and then tostop, and having provision for restoring the barrel immediately tofiring position while the bolt completes its recoil movement thereby toopen the breech for the ejection and reception of cartridges, means toprevent rotation of the barrel,

the forward portion at least of the bolt being rotatable to apredetermined degree but only while the bolt is adjacent to the firingposition, a reciprocable bolt pusher, and 'a recoil spring urging saidpusher forwardly, in combination a radial row of locking lugs on saidforward portion of the bolt which lock the bolt to the barrel in firingposition, a radial row of locking abutments carried by the barrel, arecess in the bolt behind said lugs to accommodate the lockingabutments, a cam carried by the bolt, a cam surface fixed relatively tothe frame and cooperable with the cam on the bolt to turn said forwardportion at least of the bolt from looking to unlocked position duringsaid slight rearward movement of the barrel in the frame, a second camcarried by the bolt, and a cam surface on the pusher cooperable withsaid second cam on the bolt to turn said forward portion at least of thebolt from unlocked to locking position in response to the action of saidrecoil spring while the barrel and bolt are both in exstop, and havingprovision for restoring the barrel immediately to firing position whilethe bolt completes its recoil movement thereby to open the breech forthe ejection and reception of cartridges, means to prevent rotation ofthe barrel, the forward portion at least of the bolt being rotatable toa predetermined degree, meansv operative to prevent rotation of the boltexcept when it is adjacent to the firing position, a bolt pusher, and arecoil spring urging said bolt pusher forwardly,'in combination, lockinglugs on the forward portion of the bolt, said lugs having rear surfacesin a plane substantially perpendicular to the axis of the bolt, lockingabutments carried by the barrel and which have forward surfaces in a,plane substantially perpendicular to the axis of the barrel and whichengage the aforesaid rear surfaces of said lugs when the bolt is infiring position, the bolt having a recess behind said lugs toaccommodate said abutments and being or approximately the same diameterforwardly and rearwardly of said recess, therebyto facilitate. the feedof cartridges to the firing chamber, bolt unlocking means and boltrelocking means concealed within the frame, the unlocking meansincluding cam elements, one carried by the bolt and the other by theframe, operative automatically to turn the bolt and thereby ,to unlockit from the barrel during and in response to the short recoil movementof the barrel, the relocking means including cam elements, one carriedby the pusher and one by the bolt, operative in response to advance ofthe pusher by the recoil spring to turn the bolt back to relock it tothe barrel after the barrel has been fully advanced to firing position.I

7. In a firearm of the kind wherein a barrel and a coaxially arrangedunitary breech block are mounted to recoil rearwardly in guides in asupporting frame in response to breech pressure, the barrel beingarranged to slide to a slight extent only concomitantly with the boltand then to stop, and having provision for restoring the barrelimmediately to firing position while the bolt completes its recoilmovement thereby to open the breech for the ejection and reception ofcartridges, means to prevent rotation of the barrel, the bolt beingrotatable to a predetermined degree but only while adjacent to firingposition, a reciprocatory bolt pusher, and a recoil spring normallyurging said pusher forwardly, in combination a radial row of lockinglugs on the forward portion of the bolt, a radial row of lockingabutments carried by the barrel and which en-- gage rear surfaces ofsaid lugs when the bolt is in firing position, the bolt having acircumferentially extending recess behind said lugs to accommodate theabutments, the portions of the bolt at opposite sides of the recessbeing of substantially the same diameter and cross section thereby tofacilitate the delivery of cartridges into the firing chamber, boltlocking means and bolt unlocking means concealed within the frame, theunlocking means comprising rigid, relatively movable elements,cooperable in response to recoil energy, to rotate the bolt therebyautomatically to disengage the locking lugs from the abutments duringthe short recoil of the barrel, the locking means including cooperatingrelatively movable cams, operative in response to advance movement ofthe pusher and, after the bolt has been advanced to firing position, toturn the bolt and thereby to reengage its locking lugs with the lockingabutments of the barrel.

8. In afirearm of the kind comprising a frame, a barrel mounted to slideaxially to a slight extent only in the frame, a breech bolt coaxial withthe barrel and mounted to slide rearwardly in the frame to a muchgreater extent than the barrel from firing position tocartridge-ejecting and receiving position, the bolt also being rotatableto apredetermined angular extent but only when it is adjacent to thefiring position, in combination locking means normally uniting the boltand barrel, said locking means comprising a radial row of locking lugson the forward portion of the bolt, a radial row of locking abutmentscarried by the barrel engaging the rear surfaces of the lugs when thebolt is in firing position, and means for automatically unlocking andretracting the bolt in response to recoil energy, said unlocking meanscomprising a cam surface on the bolt and a fixed cam carried by theframe, said cams being designed and arranged to rotate the bolt duringthe short concomitant recoil movement of the bolt and barrel thereby todisengage the lugs and abutments and allow axial separation of the boltfrom the barrel, means to restore the barrel to firing positionimmediately after it is released from the bolt, a pusher for restoringthe bolt to firing position, and relocking means comprising a second camsurface on the bolt and a cam carried by the pusher cooperable therewithto turn the bolt back to locking position after it has completed itsreturn movement to firing position.

MELVIN M. JOHNSON, JR.

